This invention relates generally to endoscopic camera systems and, more particularly, to a system and method for adaptive white balance for endoscopic camera systems.
Endoscopic camera systems are used for seeing inside the body of a patient. A typical endoscopic camera system has an illumination system with a light source for illuminating the inside of a body cavity and a camera for capturing images of that cavity. Endoscopic camera systems are known in which white light emitting diodes (“LED”) are used as light sources. Additionally, endoscopic systems are known in which an excitation light source, such as a blue laser emitting diode, is used to excite light from phosphors.
It is desirable to reduce the amount of input power to the illumination system for optimal camera exposure purposes, to limit the heat to a user's hand touching an endoscope and to limit heat generated at the distal tip of the endoscope. It is also desirable to reduce the amount of input power to the illumination system to reduce the size and increase the portability of the endoscope by limiting the use of mains power or substantial battery resources. Accordingly, systems are known in which drive current to a light source is reduced to the minimum possible to still obtain adequate illumination.
However, when the drive current is altered, the illumination source color may shift. For example, a color of emitted light from a white LED becomes more blue as the drive current increases. Additionally, in systems where an excitation light source is used, temperature based variation in the excitation light causes a change in efficiency of light emission from the phosphors, which results in changing volume or chromaticity of the finally produced white light. Moreover, there may be variation in drive current caused color shift among different light sources, even of the same type. Without proper color correction, resulting images may have inaccurate colors, which may make it harder for medical personnel to accurately visualize and treat a patient.
Therefore, a need exists for an improved process for allowing light source current variations while maintaining the color accuracy of the image captured by the camera system that remedies the shortcomings of the prior art.